1. Field of the Invention
The present invention relates to an image reading apparatus using a moving original method, an image forming apparatus, and an image processing apparatus.
2. Related Art
An image reading apparatus provided in an image forming apparatus such as a copying machine, a facsimile machine, or a digital multifunction peripheral, and an image reading apparatus connected to an image processing apparatus such as a computer via a communication means such as a network, are used as image reading means when, for example, based on image information output from an original reading portion that reads an original image, transferring print images to an image forming portion, transmitting print images to the image processing apparatus such as a computer (for example, a personal computer) connected to the network, and the like. Such an image processing apparatus may create prescribed image data such as PDF (Portable Document Format) data based on image information from the image reading apparatus, for example.
As conventional image reading apparatuses, many image reading apparatuses are utilized that use a moving original method in which the original reading portion reads, in a prescribed original reading position, image light from an original that is irradiated with light from a light source such as a lamp of the original reading portion while being transported in a prescribed transport direction at a prescribed transport speed by an original transport portion.
Ordinarily, such an image reading apparatus using a moving original method starts reading an original image after a reading start time set in advance has elapsed since detecting the transport timing of an original on the upstream side in the transport direction relative to the original reading position (for example, an original detecting portion such as an original detection sensor detects the downstream side edge (leading edge) in the transport direction of the original). This reading start time can be set to the time in which an original is transported from the detection position of the transport timing detected by the original detecting portion to the original reading position where reading is performed by the original reading portion, for example.
With such an image reading apparatus, when the original detecting portion and the original reading portion are attached at a factory, or when the original detecting portion and the original reading portion are adjusted or replaced by an operator such as a serviceman, due to variation in the mounting positions of the original detecting portion and the original reading portion, variation among components, and the like, the transport distance from the detection position of the transport timing detected by the original detecting portion to the original reading position where reading is performed by the original reading portion may vary between image reading apparatuses. Accordingly, ordinarily, at the time of factory shipment, or at the time of component adjustment or component replacement performed by an operator such as a serviceman, the reading start time is adjusted according to such variation.
Adjustment of the reading start time is performed by causing an image reading apparatus to be adjusted to actually transport an adjustment sheet, for example (see JP H3-158066A).
Specifically, the reading start time is adjusted so as to match a reading timing adjustment time from when the original detecting portion detects the leading edge of the adjustment sheet transported by the original transport portion on the upstream side in the transport direction relative to the original reading position until when the original reading portion reads a position considered to be the leading edge of the adjustment sheet, for example.
Further, with an image reading apparatus using a moving original method, when transport system components that constitute the original transport portion are attached at a factory, or when such transport system components are adjusted or replaced by an operator such as a serviceman, due to variation in the mounting positions of the transport system components, variation among the components, and the like, the read magnification (for example, transport speed) in the transport direction may differ from the original read magnification. Thus, ordinarily, the read magnification is adjusted at the time of factory shipment, or at the time of component adjustment or component replacement performed by an operator such as a serviceman.
This read magnification is adjusted such that, for example, a read magnification adjustment time from when the original reading portion reads a position considered to be the leading edge of an adjustment sheet until when the original reading portion reads a position considered to be the upstream side edge (trailing edge) in the transport direction of the adjustment sheet matches a reference transport time set in advance for the adjustment sheet.
However, in such an image reading apparatus using a moving original method, reading errors may occur, such as the original reading portion reading a position earlier than (before) the actual leading edge position when reading the leading edge of the adjustment sheet, or the original reading portion reading a position later than (behind) the actual trailing edge position when reading the trailing edge of the adjustment sheet. This is described below with reference to FIGS. 8A and 8B.
FIGS. 8A and 8B are schematic side views that illustrate reading errors that occur in image reading apparatuses 100′ and 100″ using a moving original method. FIG. 8A shows an example of a reading error that occurs in the image reading apparatus 100′ when a leading edge P′ of an adjustment sheet P is read by an image sensor 205 of an original reading portion 200′ in which a light source 211′ is disposed on the upstream side in a transport direction Y1, taking an original reading position R1 as a reference. FIG. 8B shows an example of a reading error that occurs in the image reading apparatus 100″ when a trailing edge P″ of the adjustment sheet P is read by an image sensor 205 of an original reading portion 200″ in which a light source 211″ is disposed on the downstream side in the transport direction Y1, taking the original reading position R1 as a reference. Further, FIG. 9 shows a state in which the light sources 211′ and 211″ are respectively disposed on the upstream side and downstream side in the transport direction Y1, taking the original reading position R1 as a reference. Note that in FIGS. 8A, 8B, and 9, reference numerals 201 and 319 respectively denote an original reading glass and reading member glass.
In the image reading apparatus 100′ shown in FIG. 8A, the light source 211′ is disposed on the upstream side in the transport direction Y1, taking the original reading position R1 as a reference, and a reading start time Ta is adjusted using a first mark Q1 on the adjustment sheet P, which has the first mark Q1 formed at least at the leading edge P′. Further, a reading member (for example, a white plate) 318 that is read by the original reading portion 200′ when an original is not being transported is provided on the side opposite to the reading side of the original reading position R1, with an original transport path 303 between the original reading portion 200′ and the reading member 318.
At least the surface of the reading member 318 is formed so as to have a lighter darkness (darkness whose difference from the darkness of the first mark Q1 can be recognized when the original reading portion 200′ performs reading (usually white)) than the first mark Q1 (usually black). In this way, when the first mark Q1 on the adjustment sheet P has not arrived, the reflected light from the reading member 318 enters the image sensor 205 of the original reading portion 200′. On the other hand, when the first mark Q1 on the adjustment sheet P has arrived, the reflected light from the first mark Q1, which is darker than the reflected light from the reading member 318, enters the image sensor 205 of the original reading portion 200′, or the reflected light from the reading member 318 is interrupted. Accordingly, the image reading apparatus 100′ can recognize the leading edge P′ of the adjustment sheet P when the position considered to be the leading edge P′ in the first mark Q1 on the adjustment sheet P is read.
Then, for adjustment using the adjustment sheet P, a reading timing adjustment time T1a is measured that is a time from when an original detection sensor 320 detects the leading edge P′ of the adjustment sheet P transported by the original transport portion (not shown) in the transport direction Y1 at a prescribed transport speed V, on the upstream side in the transport direction Y1 relative to the original reading position R1 until when the original reading portion 200′ reads a position considered to be the leading edge P′ in the first mark Q1 on the adjustment sheet P. The reading start time Ta is adjusted based on the reading timing adjustment time T1a measured in this way. For example, if the reading start time Ta is a time from when the original detection sensor 320 detects the leading edge P′ of the adjustment sheet P until when the original reading portion 200′ reads the leading edge P′ of the adjustment sheet P, the reading start time Ta is adjusted such that the reading start time Ta matches the reading timing adjustment time T1a obtained by measurement.
With such a configuration, since the light source 211′ is disposed on the upstream side in the transport direction Y1, taking the original reading position R1 as a reference, the light irradiation surface is irradiated with light L′ from the light source 211′ from a diagonally upstream side, resulting in the occurrence of shadow Na (for example, a shadow whose width is approximately 0.7 mm) at the leading edge P′ of the adjustment sheet P. Then, even though the image reading apparatus 100′ intends to read the leading edge P′ of the adjustment sheet P when reading the leading edge P′ of the adjustment sheet P in the original reading position R1, the image reading apparatus 100′ actually determines the shadow Na at the leading edge P′ of the adjustment sheet P due to the light L′ from the light source 211′ as the mark Q1, and reads a leading edge Na′ of the shadow Na as the leading edge P′ of the adjustment sheet P.
Specifically, there are problems in that even with the intention of reading the leading edge P′ of the adjustment sheet P, although the leading edge P′ of the adjustment sheet P has not been transported to the original reading position R1, the leading edge Na′ of the shadow Na at the leading edge P′ is unintentionally read earlier than the leading edge P′. In this case, the leading edge P′ of the adjustment sheet P cannot be read with sufficient accuracy when performing adjustment using the adjustment sheet P. Therefore, when reading an original, an original image cannot be read at an accurate reading start timing. Alternatively, in an image forming apparatus and an image processing apparatus to which such an image reading apparatus is connected, since image information from this image reading apparatus is shifted in the original transport direction from the normal image position, a print image is printed on a recording sheet with the printed image shifted in the transport direction from the normal image position in the image forming apparatus, or image data is created shifted in the transport direction from the normal image position in the image processing apparatus.
Note that such problems may occur in a case in which even though, as shown in FIG. 9, the light sources 211′ and 211″ are disposed respectively on both of the upstream side and the downstream side in the transport direction Y1, taking the original reading position R1 as a reference, the light amount of the light L′ from the light source 211′ on the upstream side is greater than the light amount of light L″ from the light source 211″ on the downstream side.
Further, with the image reading apparatus 100″ shown in FIG. 8B, the light source 211″ is disposed on the downstream side in the transport direction Y1, taking the original reading position R1 as a reference, and the read magnification in the transport direction Y1 is adjusted using the first mark Q1 and a second mark Q2 on the adjustment sheet P, which has the first mark Q1 formed at least at the leading edge P′, and the second mark Q2 formed at least at the trailing edge P″.
The darkness of the second mark Q2 is about the same as that of the first mark Q1 described above. Therefore, when the second mark Q2 on the adjustment sheet P has not arrived, the reflected light from the reading member 318 enters the image sensor 205 of the original reading portion 200″. On the other hand, when the second mark Q2 on the adjustment sheet P has arrived, the reflected light from the second mark Q2, which is darker than the reflected light from the reading member 318, enters the image sensor 205 of the original reading portion 200″, or the reflected light from the reading member 318 is interrupted. Accordingly, the image reading apparatus 100″ can recognize the trailing edge P″ of the adjustment sheet P when the position considered to be the trailing edge P″ in the second mark Q2 on the adjustment sheet P is read.
Then, for adjustment using the adjustment sheet P, a read magnification adjustment time T1b is measured that is a time from when the original reading portion 200″ reads a position considered to be the leading edge P′ in the first mark Q1 on the adjustment sheet P until when the original reading portion 200″ reads a position considered to be the trailing edge P″ in the second mark Q2 on the adjustment sheet P.
The read magnification is adjusted based on the read magnification adjustment time T1b measured in this way. For example, if the read magnification adjustment time T1b is shorter than a reference transport time Ts set in advance for the adjustment sheet P, the read magnification is adjusted by decreasing the transport speed V by the difference between the read magnification adjustment time T1b and the reference transport time Ts such that the read magnification matches the original read magnification. On the other hand, if the read magnification adjustment time T1b is longer than the reference transport time Ts, the read magnification is adjusted by increasing the transport speed V by the difference between the read magnification adjustment time T1b and the reference transport time Ts such that the read magnification matches the original read magnification.
With such a configuration, since the light source 211″ is disposed on the downstream side in the transport direction Y1, taking the original reading position R1 as a reference, the light irradiation surface is irradiated with the light L″ from the light source 211″ from a diagonally downstream side, resulting in the occurrence of shadow Nb (for example, a shadow whose width is approximately 0.7 mm) at the trailing edge P″ of the adjustment sheet P. Then, even though the image reading apparatus 100″ intends to read the trailing edge P″ of the adjustment sheet P when reading the trailing edge P″ of the adjustment sheet P in the reading position R1, the image reading apparatus 100″ actually determines the shadow Nb at the trailing edge P″ of the adjustment sheet P due to the light L″ from the light source 211″ as the mark Q2, and reads a trailing edge Nb″ of the shadow Nb as the trailing edge P″ of the adjustment sheet P.
Specifically, there are problems in that even with the intention of reading the trailing edge P″ of the adjustment sheet P, although the trailing edge P″ of the adjustment sheet P has already been transported to the original reading position R1, the trailing edge P″ is not read, rather, the trailing edge Nb″ of the shadow Nb at the trailing edge P″ is unintentionally read later than the trailing edge P″. In this case, the trailing edge P″ of the adjustment sheet P cannot be read with sufficient accuracy when performing adjustment using the adjustment sheet P. Therefore, when reading an original, an original image cannot be read at an accurate read magnification. Alternatively, in the image forming apparatus and the image processing apparatus to which such an image reading apparatus is connected, since image information from this image reading apparatus is different image information in the original transport direction from that read at the normal magnification, a print image is printed on a recording sheet at a different magnification in the transport direction from the normal magnification in the image forming apparatus, or image data is created at a different magnification in the transport direction from the normal magnification in the image processing apparatus.
Note that such problems may occur in a case in which even though, as shown in FIG. 9, the light sources 211′ and 211″ are disposed respectively on both of the upstream side and the downstream side in the transport direction Y1, taking the original reading position R1 as a reference, the light amount of the light L″ from the light source 211″ on the downstream side is greater than the light amount of the light L′ from the light source 211′ on the upstream side.